Dissecting the genetic basis of focal cortical dysplasia: a large cohort study
Dissecting the genetic basis of focal cortical dysplasia: a large cohort study
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DOI：
10.1007/s00401-019-02061-5
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发表时间：
2019-12-01
影响因子：
12.7
通讯作者：
Baulac, Stephanie
中科院分区：
文献类型：
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作者：
Baldassari, Sara;Ribierre, Theo;Baulac, Stephanie
遗传性皮质发育畸形（mcd），如轻度皮质发育不良（mMCD）、局灶性皮质发育不良（FCD）和半巨脑畸形（HME），是小儿神经外科手术中发生严重难治性癫痫的主要原因。FCD2以神经病理学特征为特征，包括增大的畸形神经元（DNs）和球囊细胞（bc）。在这里，我们提供了一个全面的评估生殖系和体细胞变异的贡献在一个大队列手术MCD病例。我们在一项单中心研究中招募了80例耐药癫痫患儿，术后神经病理学诊断为mMCD、FCD1、FCD2或HME。我们对匹配的血脑样本进行靶向基因测序（>= 2000X读取深度），寻找mTOR通路和FCD基因的低等位基因频率变异。我们能够阐明29%的mMCD/FCD1患者和63%的FCD2/HME患者。在mMCD/FCD1病例中发现了n -糖基化途径相关SLC35A2基因的体细胞功能丧失变异。MTOR及其激活因子（AKT3、PIK3CA、RHEB）的体细胞功能获得变异，以及其抑制因子（DEPDC5、TSC1、TSC2）的种系、体细胞和双靶功能丧失变异仅在FCD2/HME病例中被发现。我们发现面板阴性的FCD2病例显示强烈的ps6免疫染色，强调所有的FCD2都是肿瘤。微解剖细胞分析表明，dn和bc携带致病变异。我们进一步观察到病理细胞密度与变异检测可能性之间的相关性。单细胞显微解剖，随后对富集的DNs池进行测序，揭示了DEPDC5种系病例的体细胞二次撞击杂合性缺失。综上所述，本研究表明mMCD/FCD1和FCD2/HME是两种不同的遗传实体：FCD2/HME均为花叶状mtor病，而mMCD/FCD1并非由mtor通路高激活变异体引起，类似30%的病例与糖基化缺陷有关。我们为FCD/HME的有效基因检测提供了一个框架，将神经病理学与遗传发现联系起来，并强调分子评估在小儿癫痫神经外科人群中的有用性。
Genetic malformations of cortical development (MCDs), such as mild MCDs (mMCD), focal cortical dysplasia (FCD), and hemimegalencephaly (HME), are major causes of severe pediatric refractory epilepsies subjected to neurosurgery. FCD2 are characterized by neuropathological hallmarks that include enlarged dysmorphic neurons (DNs) and balloon cells (BCs). Here, we provide a comprehensive assessment of the contribution of germline and somatic variants in a large cohort of surgical MCD cases. We enrolled in a monocentric study 80 children with drug-resistant epilepsy and a postsurgical neuropathological diagnosis of mMCD, FCD1, FCD2, or HME. We performed targeted gene sequencing ( >= 2000X read depth) on matched blood-brain samples to search for low-allele frequency variants in mTOR pathway and FCD genes. We were able to elucidate 29% of mMCD/FCD1 patients and 63% of FCD2/HME patients. Somatic loss-of-function variants in the N-glycosylation pathway-associated SLC35A2 gene were found in mMCD/FCD1 cases. Somatic gain-of-function variants in MTOR and its activators (AKT3, PIK3CA, RHEB), as well as germline, somatic and two-hit loss-of-function variants in its repressors (DEPDC5, TSC1, TSC2) were found exclusively in FCD2/HME cases. We show that panel-negative FCD2 cases display strong pS6-immunostaining, stressing that all FCD2 are mTORopathies. Analysis of microdissected cells demonstrated that DNs and BCs carry the pathogenic variants. We further observed a correlation between the density of pathological cells and the variant-detection likelihood. Single-cell microdissection followed by sequencing of enriched pools of DNs unveiled a somatic second-hit loss-of-heterozygosity in a DEPDC5 germline case. In conclusion, this study indicates that mMCD/FCD1 and FCD2/HME are two distinct genetic entities: while all FCD2/HME are mosaic mTORopathies, mMCD/FCD1 are not caused by mTOR-pathway-hyperactivating variants, and similar to 30% of the cases are related to glycosylation defects. We provide a framework for efficient genetic testing in FCD/HME, linking neuropathology to genetic findings and emphasizing the usefulness of molecular evaluation in the pediatric epileptic neurosurgical population.